CN114740260A - Power-specific synchronous acquisition method for real-time detection and adjustment of crystal oscillator output frequency - Google Patents

The invention discloses a special synchronous acquisition method for electric power, which detects and adjusts the output frequency of a crystal oscillator in real time, wherein synchronous sampling based on GPS clock signals adopts fixed sampling frequency, and all sampling devices sample signals according to the fixed sampling frequency; calibrating a GPS clock signal, and triggering external interruption of the main control chip by utilizing PPS; the main control chip controls the ADC to realize sampling of first data, and simultaneously starts a timer; setting timing parameters according to a preset sampling rate, sampling a next data point after a timer controller overflows and restarting the timer, triggering sampling by using PPS (pulse per second) in GPS (global positioning system) synchronous sampling, wherein the sampling interval is determined by the setting of the timer and the frequency of a crystal oscillator; marking the UTC time label of the previous second on the measurement parameter obtained by calculation after sampling, and sending the measurement parameter to a data concentrator to complete synchronous data acquisition; the influence of the frequency error of the crystal oscillator on the synchronous sampling clock is reduced, and the production cost is saved.

实时检测并调整晶振输出频率的电力专用同步采集方法Power-specific synchronous acquisition method for real-time detection and adjustment of crystal oscillator output frequency

技术领域technical field

本发明属于同步数据采集技术领域，尤其涉及一种实时检测并调整晶振输出频率的电力专用同步采集方法。The invention belongs to the technical field of synchronous data acquisition, and in particular relates to a power-specific synchronous acquisition method for detecting and adjusting the output frequency of a crystal oscillator in real time.

背景技术Background technique

随着电力系统的发展，对全网数据进行高精度同步采样的需求变得越来迫切。GPS的出现以及其民用化，为电力系统同步测量带来了新的契机由于PPS能够提供误差在100ns以内的高精度时钟。因此，将GPS时钟信号作为异地监测装置的时间基准，能够实现各装置高精度同步采样。基于GPS时钟信号的广域测量系统通过GPS接受器解调GPS卫星信号并产生PPS和UTC时间同步信号，实现设备的同步采样和测量。针对测量数据传输过程中产生的延时，所有的测量数据均打上UTC时间标签并通过广域通信网发送至数据集中器，实现数据的存储、分析和应用。With the development of the power system, the need for high-precision synchronous sampling of the entire network data becomes more and more urgent. The emergence of GPS and its commercialization have brought new opportunities for power system synchronous measurement because PPS can provide a high-precision clock with an error of less than 100ns. Therefore, by using the GPS clock signal as the time reference of the remote monitoring devices, high-precision synchronous sampling of each device can be realized. The wide area measurement system based on the GPS clock signal demodulates the GPS satellite signal through the GPS receiver and generates the PPS and UTC time synchronization signals to realize the synchronous sampling and measurement of the equipment. In view of the delay in the transmission of measurement data, all measurement data are marked with UTC time stamp and sent to the data concentrator through the wide area communication network to realize data storage, analysis and application.

近年来，随着通信设备的普及，社会对通信设备测量仪器的需求也更加强烈，现代通信设备测量仪器中，需要精准的时钟源，来保证测量数据的精确性。由于人们在制作晶体振荡器的时候，发现晶片的切割角度对晶体振荡器的性能有着极大的影响，于是，人们进一步完善了晶振的制造工艺，晶体振荡器的发展又上升了一个层次。世界知名实验室一一贝尔实验室，宣布研制出了AT切型、5次泛音的晶体振荡器，其频率稳定度再上一个台阶。近年来，老化特性好，品质因数高的石英晶体振荡器被法国的Besancon研制出，其原理主要是严格控制工艺，降低晶振表面损耗。但是上述方式仍然会导致晶振输出频率低，不稳定。In recent years, with the popularization of communication equipment, the demand for communication equipment measuring instruments has become stronger. In modern communication equipment measuring instruments, precise clock sources are required to ensure the accuracy of measurement data. When people make crystal oscillators, they find that the cutting angle of the wafer has a great influence on the performance of crystal oscillators. Therefore, people further improve the manufacturing process of crystal oscillators, and the development of crystal oscillators has risen to a new level. Bell Labs, a world-renowned laboratory, announced that it has developed an AT-cut, 5th overtone crystal oscillator, and its frequency stability has reached a new level. In recent years, quartz crystal oscillators with good aging characteristics and high quality factor have been developed by Besancon in France. The principle is to strictly control the process and reduce the surface loss of the crystal oscillator. However, the above method will still result in a low output frequency of the crystal oscillator and instability.

而原子钟，如氢钟、铷钟、铯钟，具有很高的频率稳定度，但其售价也过高，而且环境对其性能影响很大，所以其应用范围有限，很多厂商都不会考虑去使用原子钟。Atomic clocks, such as hydrogen bells, rubidium bells, and cesium bells, have high frequency stability, but their prices are also too high, and the environment has a great impact on their performance, so their application scope is limited, and many manufacturers will not consider them. to use atomic clocks.

发明内容SUMMARY OF THE INVENTION

本发明要解决的技术问题：提供一种实时检测并调整晶振输出频率的电力专用同步采集方法，在提高输出精度的同时，降低了晶振频率误差对同步采样时钟的影响，节约了生产成本，保证了同步采样时钟的长期稳定运行The technical problem to be solved by the present invention is to provide a power-specific synchronous acquisition method for real-time detection and adjustment of the output frequency of the crystal oscillator. While improving the output accuracy, the influence of the crystal oscillator frequency error on the synchronous sampling clock is reduced, the production cost is saved, and the production cost is guaranteed. long-term stable operation of synchronized sampling clocks

本发明技术方案：Technical scheme of the present invention:

一种实时检测并调整晶振输出频率的电力专用同步采集方法，基于GPS时钟信号的同步采样采用固定采样频率，所有采样装置都按照固定采样频率对信号采样；对GPS时钟信号进行校准，利用PPS触发主控芯片的外部中断；主控芯片控制ADC实现第一个数据的采样，同时开启定时器；根据预定采样率设置定时参数，定时器控制器溢出后进行下一个数据点采样并重启定时器，GPS同步采样利用PPS触发采样，采样间隔由定时器的设置和晶体振荡器频率决定；将采样后计算得到的测量参数打上前一秒UTC时间标签，发送至数据集中器，完成数据同步采集。A power-specific synchronous acquisition method that detects and adjusts the output frequency of a crystal oscillator in real time. The synchronous sampling based on the GPS clock signal adopts a fixed sampling frequency, and all sampling devices sample the signal according to the fixed sampling frequency; the GPS clock signal is calibrated and triggered by PPS. External interrupt of the main control chip; the main control chip controls the ADC to sample the first data, and starts the timer at the same time; set the timing parameters according to the predetermined sampling rate, after the timer controller overflows, it will sample the next data point and restart the timer. GPS synchronous sampling uses PPS to trigger sampling, and the sampling interval is determined by the timer setting and the frequency of the crystal oscillator; the measurement parameters calculated after sampling are marked with the UTC time label of the previous second, and sent to the data concentrator to complete the data synchronous acquisition.

同步采样时，利用GPS接收器发出的PPS脉冲信号实现所有的采样装置都在同一个时刻开始按照同一个频率进行采样。During synchronous sampling, the PPS pulse signal sent by the GPS receiver is used to realize that all sampling devices start to sample according to the same frequency at the same time.

主控芯片控制ADC实现第一个数据的采样过程中，将脉冲所对应的ADC转换数据作为第一个有效采样数据，相邻PPS之间的所有采样时刻均由主控芯片控制。When the main control chip controls the ADC to realize the sampling process of the first data, the ADC conversion data corresponding to the pulse is taken as the first valid sampling data, and all sampling moments between adjacent PPS are controlled by the main control chip.

采样间隔为采样每秒通过PPS上升沿同步一次。The sampling interval is that the samples are synchronized once per second by the rising edge of PPS.

GPS时钟信号进行校准过程中，首先进行晶体振荡器频率的采样，再通过时间测量单元、压控晶体振荡器单元、微控制单元MCU、温度传感单元、数字模拟转换器单元DAC和电压芯片单元之间相互配合工作完成校准。In the process of calibrating the GPS clock signal, the frequency of the crystal oscillator is first sampled, and then the time measurement unit, the voltage-controlled crystal oscillator unit, the micro-control unit MCU, the temperature sensing unit, the digital-to-analog converter unit DAC and the voltage chip unit are passed. Work with each other to complete the calibration.

晶体振荡器频率的采样利用PPS作为时间基准实时测量晶振频率，自适应修正采样控制参数PRD，自适应修正采样方法包括：可变采样间隔采样、晶振输出频率实时测量及采样控制参数自适应调整。The sampling of the crystal oscillator frequency uses PPS as the time reference to measure the crystal oscillator frequency in real time, and adaptively corrects the sampling control parameter PRD. The adaptive correction sampling method includes: variable sampling interval sampling, real-time measurement of crystal oscillator output frequency, and adaptive adjustment of sampling control parameters.

可变采样间隔采样通过交替选择N_L和N_H作为定时器控制参数PRD的变间隔采样方法，利用二值选择逼近理想的脉冲计数个数N；采样控制参数自适应调整过程为：晶振输出频率实时测量、采样控制参数调整、可变采样间隔采样，利用PPS作为时间基准测量晶振输出频率并触发同步采样的首采样命令，采用可变采样间隔控制方法，根据实时监测晶振输出频率自适应调整采样控制参数。Variable sampling interval sampling By alternately selecting NL and _NH as the variable interval sampling method of timer control parameter PRD, and using binary selection to approximate the ideal number of pulse counts _N ; the adaptive adjustment process of sampling control parameters is: crystal oscillator output frequency Real-time measurement, sampling control parameter adjustment, variable sampling interval sampling, using PPS as the time reference to measure the output frequency of the crystal oscillator and trigger the first sampling command of synchronous sampling, adopt the variable sampling interval control method, and adjust the sampling adaptively according to the real-time monitoring of the crystal oscillator output frequency control parameter.

时间测量单元采用信号通过逻辑门延时来测算时间，信号通过逻辑门有一个特定的时间，此特定时间为时间测量单元的最小分辨率，start信号触发时间测量单元开始计时，stop信号触发时间测量单元停止计时，当stop有效时，粗计数器会记录下来信号通过延迟门的个数，并把结果存储在动态存储中，再经过芯片内部的ALU，进行数据的处理，算得测量的时间。The time measurement unit uses the signal to pass through the logic gate delay to measure the time. The signal passes through the logic gate for a specific time. This specific time is the minimum resolution of the time measurement unit. The start signal triggers the time measurement unit to start timing, and the stop signal triggers the time measurement. The unit stops timing. When the stop is valid, the rough counter will record the number of signals passing through the delay gate, and store the result in the dynamic storage, and then process the data through the ALU inside the chip to calculate the measured time.

微控制单元MCU通过SPI接口与外部设备进行通讯，温度传感单元通过温度传感器进行温度测量，数字模拟转换器单元DAC进行模数转换，完成输电电压大小的控制。The micro-control unit MCU communicates with external devices through the SPI interface, the temperature sensing unit performs temperature measurement through the temperature sensor, and the digital-to-analog converter unit DAC performs analog-to-digital conversion to complete the control of the transmission voltage.

电力专用同步采集过程中利用RDFT简化DFT计算量，并通过最小二乘估计法对相角序列进行多项式拟合计算信号频率,根据所得频率对原始采样序列进行重采样并迭代计算频率二次估计值，建立DFT频率偏移量与相角和幅值的误差模型，得到相角和幅值误差与频率偏移量和采样初始相位角的函数关系，通过基于准正序分量法的单相相角与幅值修正算法计算获取信号相量估计值。In the process of power-specific synchronous acquisition, RDFT is used to simplify the DFT calculation amount, and the phase angle sequence is polynomially fitted to calculate the signal frequency by the least squares estimation method, and the original sampling sequence is resampled according to the obtained frequency and iteratively calculates the secondary frequency estimate , establish the error model of DFT frequency offset and phase angle and amplitude, obtain the functional relationship between phase angle and amplitude error and frequency offset and sampling initial phase angle, through the single-phase phase angle based on the quasi-positive sequence component method Calculated with the amplitude correction algorithm to obtain the estimated value of the signal phasor.

本发明的有益效果：Beneficial effects of the present invention:

本发明在主控芯片中通过接口嵌有控制模块，通过主控芯片的控制模块实时检测并调整晶振的输出频率，根据两种不同的情况实时调整；当GPS出现抖动的情况下，利用多个PPS秒脉冲作为时间的基准，加长主控芯片定时器的时间，实时调整晶振输出频率，使实际晶振输出频率更加偏向于外部晶振的标定值；当外部晶振因为环境、时间的影响出现晶振输出频率偏差时，以每次1PPS信号为基准，利用PPS信号，每来一次PPS信号就对晶振输出频率进行一次更新，这样晶振的输出频率更加趋于标定值，使得采集频率更标准，采集的数据更准确；In the present invention, a control module is embedded in the main control chip through an interface, and the output frequency of the crystal oscillator is detected and adjusted in real time through the control module of the main control chip, and adjusted in real time according to two different situations; The PPS second pulse is used as the time reference to lengthen the timer of the main control chip and adjust the crystal oscillator output frequency in real time, so that the actual crystal oscillator output frequency is more inclined to the calibration value of the external crystal oscillator; when the external crystal oscillator is affected by the environment and time, the crystal oscillator output frequency appears When there is a deviation, based on each 1PPS signal, using the PPS signal, the output frequency of the crystal oscillator is updated every time the PPS signal comes, so that the output frequency of the crystal oscillator tends to be closer to the calibration value, making the acquisition frequency more standard and the collected data more accurate. precise;

提高输出精度的同时，降低了晶振频率误差对同步采样时钟的影响，节约了生产成本，保证了同步采样时钟的长期稳定运行。同时也可应用于其他IED设备中同步时钟的实现，为实现信息实时同步采集奠定了基础。While improving the output precision, the influence of the frequency error of the crystal oscillator on the synchronous sampling clock is reduced, the production cost is saved, and the long-term stable operation of the synchronous sampling clock is ensured. At the same time, it can also be applied to the realization of synchronous clocks in other IED devices, laying a foundation for the realization of real-time synchronous acquisition of information.

附图说明Description of drawings

图1为本发明实施例提供的TDC门电路延迟结构示意图；1 is a schematic diagram of a delay structure of a TDC gate circuit provided by an embodiment of the present invention;

图2为本发明实施例提供的温度传感器内部架构图；2 is an internal architecture diagram of a temperature sensor provided by an embodiment of the present invention;

图3为本发明实施例提供的DAC内部架构图；3 is a diagram of an internal architecture of a DAC provided by an embodiment of the present invention;

图4为本发明实施例提供的电压控制的晶体振荡器原理设计图。FIG. 4 is a schematic design diagram of a voltage-controlled crystal oscillator provided by an embodiment of the present invention.

图5为本发明实施例提供的实时检测并调整晶振输出频率的电力专用同步采集装置组成示意图。FIG. 5 is a schematic diagram of the composition of a power-specific synchronous acquisition device for real-time detection and adjustment of a crystal oscillator output frequency provided by an embodiment of the present invention.

具体实施方式Detailed ways

参考图1-图4，本实施例公开了实时检测并调整晶振输出频率的电力专用同步采集方法及相应的硬件结构，基于GPS时钟信号的同步采样通常采用固定采样频率，所有采样装置都按照固定的频率对信号采样，并利用GPS接收器发出的PPS脉冲信号保证所有的采样装置都在同一个时刻开始按照同一个频率进行采样，对GPS时钟信号进行校准，利用PPS触发主控芯片的外部中断；主控芯片控制ADC实现第一个数据的采样，同时开启定时器；根据预定采样率设置定时参数，定时器控制器溢出后进行下一个数据点采样并重启定时器，GPS同步采样利用PPS触发采样，采样间隔由定时器的设置和晶体振荡器频率决定；将采样后计算得到的测量参数打上前一秒UTC时间标签，发送至数据集中器，完成数据同步采集。1 to 4, the present embodiment discloses a power-specific synchronous acquisition method for real-time detection and adjustment of the crystal oscillator output frequency and a corresponding hardware structure. The synchronous sampling based on the GPS clock signal usually adopts a fixed sampling frequency, and all sampling devices are based on the fixed sampling frequency. The signal is sampled at the same frequency, and the PPS pulse signal sent by the GPS receiver is used to ensure that all sampling devices start sampling according to the same frequency at the same time, calibrate the GPS clock signal, and use the PPS to trigger the external interrupt of the main control chip. ;The main control chip controls the ADC to realize the sampling of the first data, and starts the timer at the same time; set the timing parameters according to the predetermined sampling rate, after the timer controller overflows, it will sample the next data point and restart the timer, and the GPS synchronous sampling is triggered by PPS Sampling, the sampling interval is determined by the timer setting and the crystal oscillator frequency; the measurement parameters calculated after sampling are marked with the UTC time label of the previous second, and sent to the data concentrator to complete the data synchronization acquisition.

图5为实时检测并调整晶振输出频率的电力专用同步采集，包括GPS模块、主控芯片、采集芯片、外部晶振以及前端驱动差分放大器，外部晶振与主控芯片连接，三相电压电流通过互感器将交流信号以差分形式输入到前端驱动差分放大器，前端驱动差分放大器获得的信号通过差分的方式输出给采集芯片，由采集芯片完成三相电压、三相电流及中心点电流的采集，采集芯片包含多通道采集入口，本实施例中采用7通道同时采集，分别采集三相电压、三相电流及中心点电流，其采集时序与GPS模块产生的PPS进行同步，将GPS模块输出秒脉冲PPS的引脚接到主控芯片，当每来1PPS信号，主控芯片中的控制模块触发一次中断，主控芯片中的定时器T2捕捉到PPS信号进入中断程序，主控芯片内部还有一个定时器T0，在定时器TO减到0时，定时器TO的输出TOUT产生一个时钟脉冲，把这个TOUT信号给主控芯片中的A/D数-模转换触发转换；在定时器T0中断函数中通过同步串行口发送当前时标，1PPS进入外部中断，在中断程序中要重载定时器T0，重新产生TOUT输出，同时新的1PPS到来，程序中断时间变量清0，重新开始新的计数；进入中断后主控芯片中的控制模块通过信号控制采集芯片开始采集数据，采集芯片采集的数据通过SPI方式与主控芯片通讯，采集芯片的数据输出口DOUT1脚与主控芯片SSP1。Figure 5 shows the power-specific synchronous acquisition for real-time detection and adjustment of the crystal oscillator output frequency, including GPS module, main control chip, acquisition chip, external crystal oscillator and front-end drive differential amplifier. The external crystal oscillator is connected to the main control chip, and the three-phase voltage and current pass through the transformer. The AC signal is input to the front-end driving differential amplifier in differential form, and the signal obtained by the front-end driving differential amplifier is output to the acquisition chip in a differential manner. The acquisition chip completes the acquisition of three-phase voltage, three-phase current and center point current. The acquisition chip includes Multi-channel acquisition entrance, in this embodiment, 7 channels are used for simultaneous acquisition, and three-phase voltage, three-phase current and center point current are collected respectively. The pin is connected to the main control chip. When a 1PPS signal comes, the control module in the main control chip triggers an interrupt. The timer T2 in the main control chip captures the PPS signal and enters the interrupt program. There is also a timer T0 in the main control chip. , when the timer TO is reduced to 0, the output TOUT of the timer TO generates a clock pulse, and the TOUT signal is sent to the A/D digital-to-analog conversion in the main control chip to trigger the conversion; in the timer T0 interrupt function, the synchronization The serial port sends the current time stamp, and 1PPS enters the external interrupt. In the interrupt program, the timer T0 should be reloaded, and the TOUT output should be regenerated. At the same time, the new 1PPS arrives, the program interrupt time variable is cleared to 0, and the new count is restarted; enter the interrupt After the control module in the main control chip controls the acquisition chip to start collecting data through signals, the data collected by the acquisition chip communicates with the main control chip through SPI, and the data output port DOUT1 of the acquisition chip communicates with the main control chip SSP1.

采集芯片数据准备好信号DRDY与主控芯片的普通I/0口连接，采集芯片的MODE[1：0]控制采集芯片的工作模式为高速模式，FORMAT[2：0]控制采集芯片的数据输出的方式为SPI模式，利用主控芯片和高精度的外部晶振产生全网同步且频率可调的采样触发脉冲即采集芯片的采样频率，该采样频率要在一个采样周期内将所有数据读走，每当数据准备好DRDY信号来时同步采集数据一次，再将采集的数据通过离散傅里叶变换DFT进行信号处理，将采集到的受谐波影响的交流信号通过离散傅里叶变换DFT将其基波提取出来，在每个采样周期内对交流信号进行采样，计算出相应于当前采样周期的基波向量，傅里叶变换后的各次谐波向量包括幅度和相位；GPS同步每次采样点，就测得各个测量单元每一个相同时刻的相位。The data acquisition chip ready signal DRDY is connected to the common I/0 port of the main control chip, the MODE[1:0] of the acquisition chip controls the working mode of the acquisition chip to be high-speed mode, and FORMAT[2:0] controls the data output of the acquisition chip The method is SPI mode, which uses the main control chip and a high-precision external crystal oscillator to generate a sampling trigger pulse that is synchronized across the network and has an adjustable frequency, that is, the sampling frequency of the acquisition chip. Whenever the data is ready for the DRDY signal, the data is collected synchronously once, and then the collected data is processed by discrete Fourier transform DFT, and the collected AC signal affected by harmonics is transformed by discrete Fourier transform DFT. The fundamental wave is extracted, the AC signal is sampled in each sampling period, and the fundamental wave vector corresponding to the current sampling period is calculated. The harmonic vectors after Fourier transform include amplitude and phase; GPS synchronizes each sampling point, the phase of each measurement unit at the same moment is measured.

由于采样频率特别高，数据量又比较大，无法实现每一点的离散傅里叶变换DFT后的结果都能及时的发送，因此采用缓存的方式，扩展了主控芯片的SDRAM作为缓存区，采用两片同步动态随机访问存储器SDRAM并联组成64M的内存容量缓存区，与主控芯片连接，用于存放DFT计算结果，缓存区满一次就传给上位机，发送结束又继续计算存储。Due to the extremely high sampling frequency and the relatively large amount of data, it is impossible to send the results of the discrete Fourier transform (DFT) at each point in time. Two pieces of synchronous dynamic random access memory SDRAM are connected in parallel to form a 64M memory capacity buffer area, which is connected to the main control chip and used to store the DFT calculation results. Once the buffer area is full, it will be transmitted to the host computer, and the calculation and storage will continue after sending.

在同步采样过程中存在多种因素导致误差，包括主控芯片定时器误差，There are many factors that cause errors in the synchronous sampling process, including the timer error of the main control chip,

相邻PPS之间的采样由主控芯片定时器控制，定时器控制可表示为：The sampling between adjacent PPS is controlled by the timer of the main control chip, and the timer control can be expressed as:

式中，f_ocs为晶振标定频率：f_s为预设采样率等于l/T，T为采样周期：N为相邻采样点之前品振发出的时钟脉冲数。理想情况下，定时器控制参数(PRD)等于晶振时钟脉冲数N，定时器计数器(Timer Counter Register，TCR)用于脉冲累加，当累加值到达PRD时触发中断并发出采样命令控制ADC采样。In the formula, f _ocs is the calibration frequency of the crystal oscillator: f _s is the preset sampling rate equal to l/T, T is the sampling period: N is the number of clock pulses sent by the oscillator before the adjacent sampling point. Ideally, the timer control parameter (PRD) is equal to the number of crystal oscillator clock pulses N, and the timer counter (Timer Counter Register, TCR) is used for pulse accumulation. When the accumulated value reaches the PRD, an interrupt is triggered and a sampling command is issued to control ADC sampling.

在实际应用中，由于晶振频率选择的局限性，晶振频率通常不是理想采样频率的整数倍，即N含有小数部分，而主控芯片的PRD只能设置成整数，由于N非整除引起的残余部分将导致采样间隔误差。N的小数部分(Fraction Part，FP)可表示为In practical applications, due to the limitation of crystal oscillator frequency selection, the crystal oscillator frequency is usually not an integer multiple of the ideal sampling frequency, that is, N contains a fractional part, and the PRD of the main control chip can only be set to an integer. will result in sampling interval errors. The fractional part (FP) of N can be expressed as

FP＝N-Floor(N)FP=N-Floor(N)

式中，Floor(N)为向下取整函数。设i和Ny分别为N相邻的整数，即In the formula, Floor(N) is the round-down function. Let i and Ny be N adjacent integers respectively, namely

N_L＝Floor(N)N _L = Floor (N)

N_L+1＝N_H NL +1 _{= NH}

传统采样控制中，PRD通常设置成Nu或者NA。然而，无论PRD设置成N_L或者Ny都将产生由残余部分引起的采样间隔误差。设单个采样点的采样时间误差为：In traditional sampling control, PRD is usually set to Nu or NA. However, no matter if PRD is set to _NL or Ny, a sampling interval error caused by the residual will be generated. Let the sampling time error of a single sampling point be:

由采样间隔误差引起的相角测量误差为：The phase angle measurement error caused by the sampling interval error is:

ε_a＝360°×t_error×f₀ ε _a =360°×t _error ×f ₀

式中f₀为电网频率，where f ₀ is the grid frequency,

设标定晶振频率为200MHz，理想采样频率为1440Hz，电网频率为60Hz。单个采样点时间误差为0.44us，相角误差为(1.31×10-3)。Set the calibrated crystal frequency to 200MHz, the ideal sampling frequency to 1440Hz, and the grid frequency to 60Hz. The time error of a single sampling point is 0.44us, and the phase angle error is (1.31×10-3).

此误差在实际应用中可忽略不计。然而，相角误差将在两邻PPS内随时间累积，其最大累积误差分别达到644us和1.88°，此误差已超出电力系统同步相角测量的最大允许误差。This error is negligible in practical applications. However, the phase angle error will accumulate over time in the two adjacent PPS, and the maximum accumulated error reaches 644us and 1.88°, respectively, which exceeds the maximum allowable error of the synchronization phase angle measurement of the power system.

由于频率可定义为相角的导数，频率测量可由相角序列计算出相角变化率得到，所以频率误差可表示为：Since the frequency can be defined as the derivative of the phase angle, the frequency measurement can be obtained by calculating the phase angle change rate from the phase angle sequence, so the frequency error can be expressed as:

可见线性累积相角误差将引起频率的直流偏置误差。设PRD设置为Ny，一秒内的因非整除引起采样误差。x(k)和x*(k)分别为理想和实际采样序列。K为每秒采样个数。由于首采样点由PPS触发，x(0)和x*(0)重合。由于晶振频率f_ocs是采样频率，的非整数倍，实际采样间隔不等于理想采样间隔，从第二个采样点开始，有It can be seen that the linear cumulative phase angle error will cause the DC offset error of the frequency. Let PRD be set to Ny, the sampling error due to non-division within one second. x(k) and x*(k) are ideal and actual sampling sequences, respectively. K is the number of samples per second. Since the first sample point is triggered by PPS, x(0) and x*(0) coincide. Since the crystal oscillator frequency f _ocs is a non-integer multiple of the sampling frequency, the actual sampling interval is not equal to the ideal sampling interval. Starting from the second sampling point, there are

λ_{(1)_H}＝T-Ts≠0λ _{(1)_H} =T-Ts≠0

设输入信号为理想的60Hz正弦信号。采样时间误差引起的测量相角和频率误差可见，相角误差的变化趋势与采样时间误差类似。Let the input signal be an ideal 60Hz sinusoidal signal. The measurement phase angle and frequency errors caused by the sampling time error can be seen, and the change trend of the phase angle error is similar to that of the sampling time error.

对于i和Ny，其相角误差偏移方向相反。线性相角偏移将引起频率的直流偏置D1和D2。由于PPS秒脉冲信号的误差清零作用，相角误差在PPS处发生突变。设频率在测量在短时间内保持恒定，相角序列应保持连续。因此，当相角序列窗口滑动至每秒末将包含相角断点，该断点将导致频率的尖峰误差，尖峰的宽度等于用于计算频率的相角序列窗口长度。For i and Ny, the phase angle errors are shifted in opposite directions. A linear phase angle offset will cause a DC offset of the frequency D1 and D2. Due to the error clearing function of the PPS second pulse signal, the phase angle error has a sudden change at the PPS. Assuming that the frequency remains constant for a short period of time during the measurement, the phase angle sequence should remain continuous. Therefore, when the phase angle sequence window slides to the end of every second, it will contain a phase angle breakpoint, which will cause a spike error in frequency, and the width of the spike is equal to the length of the phase angle sequence window used to calculate the frequency.

主控芯片控制ADC实现第一个数据的采样过程中，将脉冲所对应的ADC转换数据作为第一个有效采样数据，相邻PPS之间的所有采样时刻均由主控芯片控制；采样间隔为采样每秒通过PPS上升沿同步一次，以消除主控芯片中晶振偏移引起的积累误差。When the main control chip controls the ADC to realize the sampling process of the first data, the ADC conversion data corresponding to the pulse is taken as the first valid sampling data, and all sampling moments between adjacent PPS are controlled by the main control chip; the sampling interval is Sampling is synchronized once per second by the rising edge of PPS to eliminate accumulated errors caused by crystal oscillator offsets in the main control chip.

GPS时钟信号进行校准过程中，首先进行晶体振荡器频率的采样，再依赖时间测量单元、压控晶体振荡器单元、微控制单元MCU、温度传感单元、数字模拟转换器单元DAC、电压芯片单元之间相互配合工作完成校准。晶体振荡器频率的采样过程中利用高精度PPS作为时间基准实时测量晶振频率，自适应修正采样控制参数PRD，抑制由晶振频率偏移而引起的残余误差，提高同步采样的抗扰性和稳定性，自适应同步采样方法主要包括：可变采样间隔采样、晶振输出频率实时测量及采样控制参数自适应调整。In the process of calibrating the GPS clock signal, the frequency of the crystal oscillator is first sampled, and then it depends on the time measurement unit, the voltage-controlled crystal oscillator unit, the microcontroller unit MCU, the temperature sensing unit, the digital-to-analog converter unit DAC, and the voltage chip unit. Work with each other to complete the calibration. In the sampling process of the crystal oscillator frequency, the high-precision PPS is used as the time reference to measure the crystal oscillator frequency in real time, and the sampling control parameter PRD is adaptively corrected to suppress the residual error caused by the crystal oscillator frequency offset, and improve the immunity and stability of synchronous sampling. , the adaptive synchronous sampling method mainly includes: variable sampling interval sampling, real-time measurement of crystal oscillator output frequency and adaptive adjustment of sampling control parameters.

所述可变采样间隔采样提出通过交替选择N_L和N_H作为定时器控制参数PRD的变间隔采样方法，利用二值选择逼近理想的脉冲计数个数N；所述晶振输出频率实时测量晶振随着工作时间的增加、外界环境温度的变化，其输出频率ft将偏移其标定值fosc，而基于GPS的同步采样中，PPS信号负责采样的同步，晶振的输出频率直接决定同步采样间隔，实时监测晶振的输出频率，能提高采样间隔控制的准确性；所述采样控制参数自适应调整过程为：晶振输出频率实时测量、采样控制参数调整、可变采样间隔采样，利用高精度PPS作为时间基准测量晶振输出频率并触发同步采样的首采样命令，采用可变采样间隔控制方法，根据实时监测晶振输出频率自适应调整采样控制参数。The variable sampling interval sampling proposes a variable interval sampling method by alternately selecting NL and _NH as the timer control parameter PRD, and using binary selection to approximate the ideal number of pulse counts _N ; With the increase of the working time and the change of the ambient temperature, the output frequency ft will offset its calibration value fosc. In the GPS-based synchronous sampling, the PPS signal is responsible for the synchronization of the sampling, and the output frequency of the crystal oscillator directly determines the synchronous sampling interval. Monitoring the output frequency of the crystal oscillator can improve the accuracy of sampling interval control; the adaptive adjustment process of the sampling control parameters is: real-time measurement of the crystal oscillator output frequency, adjustment of sampling control parameters, sampling at variable sampling intervals, and using high-precision PPS as a time reference Measure the output frequency of the crystal oscillator and trigger the first sampling command of synchronous sampling, adopt the variable sampling interval control method, and adjust the sampling control parameters adaptively according to the real-time monitoring of the output frequency of the crystal oscillator.

晶振输出频率检测方法中晶振随着工作时间的增加、外界环境温度的变化，其输出频率i将偏移其标定值fosc。而基于GPS的同步采样中，PPS信号负责采样的同步，晶振的输出频率直接决定同步采样间隔，若能实时监测晶振的输出频率，能提高采样间隔控制的准确性。In the crystal oscillator output frequency detection method, with the increase of the working time and the change of the external environment temperature, the output frequency i of the crystal oscillator will deviate from its calibration value fosc. In GPS-based synchronous sampling, the PPS signal is responsible for the synchronization of sampling, and the output frequency of the crystal oscillator directly determines the synchronous sampling interval. If the output frequency of the crystal oscillator can be monitored in real time, the accuracy of sampling interval control can be improved.

在稳定的GPS卫星信号接收情况下，GPS接收器可提供精确度ns级且无累积误差的PPS秒脉冲，以PPS为基准信号，可实时监测晶振输出频率，调整采样控制参数，实现自适应采样周期信号的频率定义为单位时间内周期信号所含的周期个数：In the case of stable GPS satellite signal reception, the GPS receiver can provide PPS second pulses with ns-level accuracy and no accumulated error. With PPS as the reference signal, the output frequency of the crystal oscillator can be monitored in real time, and the sampling control parameters can be adjusted to achieve adaptive sampling. The frequency of a periodic signal is defined as the number of cycles contained in the periodic signal per unit time:

f＝n/tf=n/t

式中，n为周期信号在时间间隔t中的周期数。用计数器测量周期信号的周期数n，再除以这些周期数所经历的时间t，就得到了周期信号的频率f。In the formula, n is the number of cycles of the periodic signal in the time interval t. The frequency f of the periodic signal is obtained by measuring the number of cycles n of the periodic signal with a counter, and dividing it by the time t elapsed by these cycles.

晶振的短期稳定性较好，设晶振输出频率f在一秒内保持恒定。以PPS时间信号为基准，测量相邻lPPS信号间隔定时器的脉冲数可得定时计数器的计数频率。由于文中计数器的计数频率是由晶振频率经过倍频后得到的，由计数器的计数频率除以倍频数后得到晶振工作的频率。设y位主控芯片的标称晶振频率为fosc，其定时器最长定时时间fmar为：The short-term stability of the crystal oscillator is better, and the output frequency f of the crystal oscillator is set to remain constant within one second. Taking the PPS time signal as the benchmark, the counting frequency of the timer counter can be obtained by measuring the number of pulses of the adjacent lPPS signal interval timer. Since the counting frequency of the counter is obtained by multiplying the frequency of the crystal oscillator, the working frequency of the crystal oscillator is obtained by dividing the counting frequency of the counter by the frequency multiplier. Let the nominal crystal frequency of the y-bit master chip be fosc, and the longest timer time fmar of the timer is:

t_max＝2^y/(f_osc×P)t _max =2 ^y /( _fosc ×P)

式中，P为系统倍频系数。当t_max小于1秒，定时器需设置为自动清零和重启模式。以PPS信号的上升作为外部中断信号，读取相邻PPS中断时计数器的值Wi和W2，晶振的实际输出频率ft可表示为：In the formula, P is the system frequency multiplication coefficient. When t _max is less than 1 second, the timer needs to be set to auto-clear and restart mode. Taking the rise of the PPS signal as the external interrupt signal, and reading the values Wi and W2 of the counter when the adjacent PPS is interrupted, the actual output frequency ft of the crystal oscillator can be expressed as:

式中，G为定时器溢出重启的次数。In the formula, G is the number of times the timer overflows and restarts.

利用PPS信号，f_t每秒实时更新，将有效消除晶振频率偏移对同步采样影响。修正后t时刻采样控制参数Mo和FPn分别为：Using the PPS signal, f _t is updated in real time every second, which will effectively eliminate the influence of crystal oscillator frequency offset on synchronous sampling. After the correction, the sampling control parameters Mo and FPn at time t are:

FP_(t)＝N_(t)-Floor(N_(t))FP _(t) = N _(t) - Floor (N _(t) )

实际PPS信号含有零均值的随机误差，虽然具有长期稳定性，但其在短期会有抖动，一般有几百ns。为减小PPS短期抖动对晶振频率测量的影响，可利用多个PPS秒脉冲作为时间基准，既延长计数器计数时间。设采用连续m个PPS秒，脉冲作为时间基准，则晶振输出频率为：The actual PPS signal contains random errors with zero mean value. Although it has long-term stability, it will have jitter in the short term, generally several hundred ns. In order to reduce the impact of PPS short-term jitter on the crystal oscillator frequency measurement, multiple PPS second pulses can be used as the time reference, which prolongs the counting time of the counter. Assuming that continuous m PPS seconds are used and the pulse is used as the time reference, the output frequency of the crystal oscillator is:

式中，G_m为m个PPS间定时器溢出重启的次数。In the formula, G _m is the number of timer overflow restarts between m PPSs.

自适应同步采样方法主要包括：晶振输出频率实时测量、采样控制参数调整、可变采样间隔采样。利用高精度PPS作为时间基准测量晶振输出频率并触发同步采样的首采样命令，采用可变采样间隔控制方法，根据实时监测晶振输出频率自适应调整采样控制参数，其具体步骤如下：The adaptive synchronous sampling method mainly includes: real-time measurement of crystal oscillator output frequency, adjustment of sampling control parameters, and variable sampling interval sampling. Using high-precision PPS as the time reference to measure the output frequency of the crystal oscillator and trigger the first sampling command of synchronous sampling, the variable sampling interval control method is adopted, and the sampling control parameters are adaptively adjusted according to the real-time monitoring of the crystal oscillator output frequency. The specific steps are as follows:

(1)得到t时刻实时晶振输出频率ft；(1) Obtain the real-time crystal oscillator output frequency ft at time t;

(2)得到理想采样控制参数N_(t)及其小数部分FP_(t)；(2) obtain the ideal sampling control parameter N _(t) and its fractional part FP _(t) ;

(3)利用PPS触发外部中断，触发首采样；(3) Use PPS to trigger an external interrupt to trigger the first sampling;

(4)确定N_L和N_H的选择规则，确定第k个点采样控制参数；(4) Determine the selection rules of _NL and _NH , and determine the sampling control parameter of the kth point;

(5)更新vk，选择规则，返回步骤(4)，直至完成一秒内所有采样。(5) Update vk, select a rule, and return to step (4) until all samples within one second are completed.

电网同步采集过程中利用RDFT简化DFT计算量，并通过最小二乘估计法对相角序列进行多项式拟合计算信号频率，根据所得频率估计值，对原始采样序列进行重采样并迭代计算频率二次估计值，提高频率的测量精度，建立DFT频率偏移量与相角和幅值的误差模型，得到相角和幅值误差与频率偏移量和采样初始相位角的函数关系，通过基于准正序分量法的单相相角与幅值修正算法，在基波频率波动剧烈、高斯白噪声、谐波、闪变存在、频率偏移程度较大、非平稳信号的情况下，通过较少的计算量获取信号相量估计值。电网同步采集基于RDFT频率测量算法得到修正采样序列，对频率进行二次评估，具体包括频率测量计算，信号的重采样及频率再估计，完成修正。In the process of power grid synchronization acquisition, RDFT is used to simplify the DFT calculation amount, and the least squares estimation method is used to perform polynomial fitting on the phase angle sequence to calculate the signal frequency. According to the obtained frequency estimation value, the original sampling sequence is resampled and the frequency is calculated twice by iteration Estimate the value, improve the measurement accuracy of the frequency, establish the error model of the DFT frequency offset and the phase angle and amplitude, and obtain the functional relationship between the phase angle and amplitude error and the frequency offset and the sampling initial phase angle. The single-phase phase angle and amplitude correction algorithm of the sequence component method, in the case of severe fundamental frequency fluctuations, Gaussian white noise, harmonics, flicker, large frequency offset, and non-stationary signals, through less The amount of computation obtains an estimate of the signal phasor. The synchronous acquisition of the power grid is based on the RDFT frequency measurement algorithm to obtain the corrected sampling sequence, and the frequency is evaluated twice, including frequency measurement calculation, signal resampling and frequency re-estimation, and the correction is completed.